This invention relates in general to friction clutches for vehicles. In particular, this invention relates to an apparatus for automatically sensing when the friction elements of a clutch are excessively worn and, in response thereto, generating an indication to the driver of the vehicle of such wear.
Clutches are well known devices which are frequently employed in vehicles to selectively connect a source of rotational power, such as the crankshaft of an engine, to a driven mechanism, such as a transmission. Typically, a cover of the clutch is connected to a flywheel carried on the end of the engine crankshaft for rotation therewith. Between the flywheel and the clutch cover, a pressure plate is disposed. The pressure plate is connected for rotation with the flywheel and the cover, but is permitted to move axially relative thereto. A release bearing is connected to the pressure plate such that axial movement of the release bearing causes corresponding axial movement of the pressure plate.
A driven disc assembly is disposed between the pressure plate and the flywheel. The driven disc assembly is carried on an output shaft of the clutch, which forms the input to the transmission. Means are provided for selectively moving the release bearing (and, therefore, the pressure plate) back and forth in the axial direction. When the pressure plate is moved toward the flywheel, the driven disc assembly is frictionally engaged therebetween so as to cause the output shaft of the clutch to rotate with the flywheel, the cover, and the pressure plate. When the pressure plate is moved away from the flywheel, the driven disc assembly is released from such frictional engagement so as to disconnect this driving connection.
The driven disc assembly typically includes a hub which is splined onto the output shaft of the clutch for rotation therewith. A generally annular support plate is mounted on the hub for limited relative rotational movement. A plurality of friction elements are usually secured to the outer radial portions of the support plate. These friction elements are repeatedly engaged and disengaged by the pressure plate and the flywheel as the clutch is operated. When the clutch is new, the friction elements have a predetermined thickness. However, each time the clutch is engaged, the friction elements wear slightly thinner. After a certain amount of use, the thickness of the friction elements will have worn so thin that the clutch may not operated properly.
To compensate for such wear, many clutches are provided with a wear compensating structure which adjusts the internal components thereof as wear occurs. Some of such wear compensating structures operate manually, while others operate automatically. However, in both instances, the friction elements will eventually wear so thin that further compensating adjustment is not available. Because the friction elements are disposed internally within the clutch, it is difficult to inspect them, visually or otherwise, to determine if they have become excessively worn. Accordingly, it would be desirable to provide an apparatus for automatically sensing when the friction elements of a clutch are excessively worn and, in response thereto, generating an indication to the driver of the vehicle of such wear.